This invention relates to switched reluctance motors and, more particularly, to a switched reluctance motor having redundant poles to reduce the "ovalizing" effects on the motor's structure and the noise generated thereby.
In U.S. patent application 747,855, which is assigned to the same assignee as the present application, there is disclosed a shifted pole, single phase variable reluctance motor. One of the problems addressed by the invention disclosed in this co-pending application is noise generated by motor "ovalizing". This problem arises because the motor's stator and rotor assemblies are usually installed in the same frame. As a result, mechanical forces are created within the assembly as the rotor and stator poles come into and go out of alignment. Thus, when poles align, the assembly is subjected to an inward (pulling) force. When the poles reach 90 degrees out of alignment, an outward (pushing) force is produced. The consequent distortion changes the normal circular (in cross-section) motor structure into an oval shape. Flexure of the motor structure, caused by this distortion, produces noise which can reach undesirably high levels.
The structure disclosed in the co-pending application helps alleviate this problem in a single phase, unidirectional motor. The problem, however, exists for other type motors as well. In this regard, other approaches to solving the ovalizing problem have been used. See, for example, U. S. Pat. No. 4,998,052. The present invention advances the solution to the ovalizing problem addressed by applicant's own previous work and that disclosed in this '052 patent so that a solution to this problem is now available for poly-phase, bi-directional switched reluctance motors as well as for variable reluctance motor's of the type described in the co-pending application.